Prediction markets, the online platforms where people buy and sell shares tied to the outcome of future events, are booming. Combined monthly trading volume on the two biggest, Kalshi and Polymarket, hit $53 billion in July, more than double what it was in May.

Americans can bet on something as low stakes as whether President Donald Trump will say "sleepy Joe" this week or as high stakes as who will control Congress. CNN runs a live Kalshi ticker during segments that feature the data, while CNBC and Fox have signed their own deals with the company, just in time for the midterm elections.

The more mainstream these markets become, the more they invite corruption. Candidates and campaign staffers can profit from information the public doesn't have, such as an internal poll or a decision to drop out of a race. And now that the odds are on TV, anyone with enough money has a reason to try to move them.

Should insiders be allowed to bet on unreleased information?

Prediction markets do have value. Because people put money behind their predictions, the price a market settles on reflects what bettors actually believe and how confident they are. That often makes it a decent read on how likely something is to happen.

But they're also ripe for abuse. The major prediction markets say they ban insider trading, or betting on information the public doesn't have, but when the stakes are this high, somebody will always........

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